In folding blade knives, such as the well known "Swiss army" type knives, the cutting blade is pivotally carried at one end of the knife handle. To extend the blade from its retracted position, or to retract or "fold" the blade from its extended position, it is usually required for the user to grasp the handle with one hand, while the cutting blade is edge wisely held at its back edge between a few fingers of the user's other hand. Accordingly, the two hands of the user are usually required for handling these types of knives. Such an arrangement is not suitable for use by hunters, workmen, sailors and the like who must use one hand for holding the article and thereby leaving free a single hand to open a folded knife blade. It would be preferable if one hand could remain free at all times, for convenience.
U.S. Pat. No. 4,095,337 issued Jun. 20, 1978 to Cecil PHARR, discloses a folding blade lock knife that includes means for opening the blade on the handle with a single hand. These means consist of a U-shape bracket, being anchored edge wisely to the back edge of the blade, and carrying a transverse manual arm. A user may then hold the knife handle in his hand palm and with a few fingers of the same hand, while the thumb of that same hand may push the transverse arm to extend the blade from its folded position; folding of an extended blade is done in the usual fashion.
One problem with the PHARR patent is that two inverted versions of the folding blade knife are required, since the folding arm as installed for a left-handed person must be reversed for use by a right-handed person (see column 3, lines 20-28 of the specification). Another inconvenience with the PHARR folding blade knife is that a separate element must be added and attached edgewisely to the back edge of the blade, thus undesirably adding a blade thickening portion which would compromise deep cutting knife action with the extended blade.
In U.S. Pat. No. 4,347,665 issued 7 Sep. 1982 to Louis LESSER, there is disclosed a folding blade knife with the blade thereof being openable through the use of a single hand. A so-called liner lock blade locking mechanism is provided, for holding the blade in an extended operative position. The liner lock consists of a leaf spring arranged so that one end is attached to the spacer portion of the knife handle side portion by an interference fit in a corresponding slot, so that the spring cantilevers outwardly into a cavity of a blade inner cam. The leaf spring opens through and can be manually accessed via an aperture made in the knife handle. The leaf spring is arcuate to provide a normal bias against the underside of the lever of the blade inner cam. The cam causes the latch of the lever mechanism to drop into a corresponding notch made radially of inner cam.
A disadvantage of the LESSER patent is that, for extending the blade, the user still needs to grasp with his thumb an aperture boss at the back edge portion of the blade. The present inventor does not consider such blade extension method economically satisfactory, since the blade-contacting thumb needs to be much extended beyond the handle body and enter into an uncomfortable translational motion, leading to in comfort of the user.
Other known folding blade lock knives include a knife sold under the trademark LEOPARD CUB, manufactured and sold in the United States by the American corporation Bench made, Inc. Folding of the extended blade of the LEOPARD knife is again claimed to be a single-hand operation, being done by manually grasping a radial thumb lug opening stud, which transversely projects from the back edge portion of the knife blade proximate the pivotal mount thereof on the knife handle. Again, it is believed that the ergonomics involved in holding the knife handle and in pivoting the lug stud, both with the same single hand, could be improved, for comfort of the user.